In my experience as a math tutor, they’re untaught natural abilities via poorly constructed (and hence, understandably confusing) “math” lessons taught by human

In my experience as a math tutor, they’re untaught natural abilities via poorly constructed (and hence, understandably confusing) “math” lessons taught by humanities majors turned primary school teacher. I often make the same point, and have occasionally found just rewriting it as “4 + [x] = 9” is enough to help span the conceptual bridge. Sticky notes in white board equations is another way to make this point.